ABSTRACT Environmental noise is harmful to quantum technologies, but structured environments can temporarily store and return information, producing useful memory effects. We study this mechanism in a microscopic qubit pseudomode model, where a qubit couples to a single damped mode. Although the enlarged qubit–pseudomode dynamics is Markovian, the reduced qubit channel crosses from CP‐divisible‐like to CP‐indivisible‐like regimes as the coupling , damping , and detuning are varied. Using a trace‐distance backflow proxy together with the amplitude‐damping CP‐divisibility criterion, equivalently Choi positivity of intermediate maps, we construct a finite‐window memory map. The backflow proxy is a restricted diagnostic based on selected state pairs, not a faithful estimate of the optimized BLP measure. This map organizes two task‐level benchmarks. In hybrid qubit–qutrit transmission, we use an established RHP‐type entanglement‐revival benchmark; the qutrit is only a passive embedded reference, and qubit–qubit checks confirm channel‐level revivals. In detuning metrology, the quantum Fisher information provides multiple interrogation windows under a time‐budgeted two‐time protocol with the same channel uses as a single‐time baseline. The protocol assumes ideal fresh environments with no reset‐time cost. Overall, the results link pseudomode memory to entanglement preservation and parameter estimation without claiming a full resource theory.
ABSTRACT Environmental noise is harmful to quantum technologies, but structured environments can temporarily store and return information, producing useful memory effects. We study this mechanism in a microscopic qubit pseudomode model, where a qubit couples to a single damped mode. Although the enlarged qubit–pseudomode dynamics is Markovian, the reduced qubit channel crosses from CP‐divisible‐like to CP‐indivisible‐like regimes as the coupling , damping , and detuning are varied. Using a trace‐distance backflow proxy together with the amplitude‐damping CP‐divisibility criterion, equivalently Choi positivity of intermediate maps, we construct a finite‐window memory map. The backflow proxy is a restricted diagnostic based on selected state pairs, not a faithful estimate of the optimized BLP measure. This map organizes two task‐level benchmarks. In hybrid qubit–qutrit transmission, we use an established RHP‐type entanglement‐revival benchmark; the qutrit is only a passive embedded reference, and qubit–qubit checks confirm channel‐level revivals. In detuning metrology, the quantum Fisher information provides multiple interrogation windows under a time‐budgeted two‐time protocol with the same channel uses as a single‐time baseline. The protocol assumes ideal fresh environments with no reset‐time cost. Overall, the results link pseudomode memory to entanglement preservation and parameter estimation without claiming a full resource theory.
Accurate noise characterization is essential for scaling quantum processors toward fault-tolerant operation. Although reduced qubit dynamics are often modeled with Markovian master equations, present-day devices can exhibit memory effects generated by residual qubit-qubit couplings, structured environments, and finite bath correlation times. Here we develop a channel-resolved, Post-Markovian Master Equation model for non-Markovian noise and test it in superconducting qubits. Using idle-evolution tomography on IBM Quantum processors, we identify complementary operational signatures of non-Markovianity, including violations of CP-divisibility and revivals of distinguishability-based information-backflow measures. We further derive a closed-form spectator-ZZ model with local dissipation and show that it captures the observed transverse Bloch-vector revivals while leaving the longitudinal relaxation mode Markovian within the model. The fitted closed-form dynamics enable an analytical reconstruction of the transverse memory kernel, whose damped oscillatory structure captures the non-Markovian correction beyond the fitted Markovian baseline. Two-qubit tomography shows buildup and revivals of quantum mutual information on comparable timescales, supporting spectator-induced crosstalk as an important contributor to the observed memory effects. Our results connect operational non-Markovianity diagnostics, microscopic crosstalk modeling, and reduced memory-kernel reconstruction in a single experimental framework for superconducting quantum hardware.
Abstract Non-Markovian dynamics is central to quantum information processing, as memory effects strongly influence coherence preservation, metrology, and communication. In this work, we investigate the role of stochastic system–bath couplings in shaping non-Markovian behavior of open quantum systems, using the central spin model within a time-convolutionless master equation framework. We show that the character of the reduced dynamics depends jointly on the intrinsic memory of the environment and on the structure of the system–environment interaction. In certain regimes, the dynamics simplify to pure dephasing, while in general both amplitude damping and dephasing contribute to the evolution. By employing two complementary measures: the Quantum Fisher Information (QFI) flow and the Breuer–Laine–Piilo (BLP) measure, we demonstrate that QFI flow may fail to witness memory effects in weak-coupling and near-resonant regimes, whereas the BLP measure still detects information backflow. Furthermore, external modulation of the interaction kernel produces qualitatively richer behavior, including irregular and frequency-dependent revivals of non-Markovianity. These results clarify the physical origin of memory effects, highlight the limitations of single-witness approaches, and suggest that stochasticity and modulation can be harnessed to engineer robust, noise-resilient quantum technologies.
We study the dissipative dynamics of a hybrid qubit–qutrit system initially prepared in the interacting thermal (Gibbs) state of the full Hamiltonian and subsequently subjected to a non-Markovian amplitude-damping channel. To benchmark the persistence of nonclassical features in this noisy setting, we track four complementary quantum resources: entanglement via negativity (NEG), nonclassical correlations via geometric quantum discord (GQD), coherence via the [Formula: see text]-norm of coherence (LNC) and measurement-induced quantumness via local quantum uncertainty (LQU). We show that coherent exchange coupling g enhances both the initial magnitudes and lifetimes of all resources by strengthening qubit–qutrit hybridization, whereas strong dispersive (cross-Kerr) coupling [Formula: see text] suppresses thermal correlations already at [Formula: see text], thereby limiting the resources available before dissipation sets in. Environmental memory effects, controlled by the reservoir cutoff frequency, slow the decay and can induce some revival pattern–assisted decay, extending the operational time window slightly. Across a broad parameter range, coherence (LNC) is consistently the most robust resource, often persisting after entanglement and discord have decayed, indicating that coherence-based protocols may provide superior stability in noisy hybrid architectures.
We study a system qubit repeatedly interacting with the same environmental qubit, with a reservoir acting on the environment between collisions via a completely positive, trace-preserving map. We show that complete suppression of system--environment correlations uniquely requires a full environmental reset, recovering a semi group dynamics with a time-independent Gorini--Kossakowski--Sudarshan--Lindblad generator, whereas a partial reset yields a continuous transition between Markovian and non-Markovian regimes governed by a single dimensionless relaxation parameter. For a resonant excitation-exchange interaction, we obtain exact closed-form expressions for the Bloch-vector dynamics for both a generalized depolarizing channel and a generalized amplitude-damping channel acting as the reservoir-induced map. Using the Breuer--Laine--Piilo measure and a Choi-matrix CP-divisibility witness, we identify three distinct dynamical regimes across the parameter space: CP-divisible Markovian dynamics, CP-indivisible but P-divisible dynamics, and non-P-divisible non-Markovian dynamics. The boundaries between these regimes, and the structural differences between uniform and anisotropic environmental relaxation, are characterized numerically.
Abstract Digital quantum simulation of open quantum systems has produced a range of methods for reproducing non-Markovian dynamics, including pseudomode embeddings, the hierarchical equations of motion, and collision models. These methods are validated against populations, coherences, or spectra. They are not validated against the quantities that define memory itself, and the behavior of those quantities under the pressures of a real simulation is largely unexamined. We study three such pressures. First, a single-qubit mode encoding misrepresents the Breuer-Laine-Piilo (BLP) measure with an error whose sign flips between regimes: it fabricates memory at strong coupling, by about a factor of 2.6 over the converged value, and it erases memory at moderate temperature. The Rivas-Huelga-Plenio (RHP) measure corroborates the temperature-driven destruction, while at strong coupling it is numerically unstable and does not track the BLP result. We derive a cross-validated rule for the required Fock dimension that collapses both regimes onto the occupied number extent, d req ≈ ⌈⟨n⟩+c σ n ⌉+1, and we show that the constant must be calibrated on super-Poissonian statistics. Second, using the exact noisy measure as computable ground truth, we show that the raw finite-shot estimate of the BLP measure can nearly double the true value under realistic noise. We provide a debiased estimator that is validated near-unbiased in that regime, together with a Markovian null-floor control that ports to hardware. Third, temporally correlated device noise is conflated with physical memory by the measure. A resource-fair comparison finds that a pseudomode and an ancilla-train collision model reach parity at equal qubit cost for a single-Lorentzian bath. Every result is simulator-based, validated against an exact reference, and reproducible from recorded data. We make no claim of quantum advantage.
ABSTRACT Quantum entanglement enables advanced quantum technologies, including secure communication and quantum computing. This study investigates the temporal dynamics of GHZ‐type entangled states in a three‐photon system subjected to pure environmental dephasing noise. We distinguish between Markovian regimes, characterized by memoryless decay, and non‐Markovian regimes, where environmental memory effects induce information backflow and can generate revivals of non‐separable quantum correlations. Employing genuine multipartite concurrence to quantify genuine tripartite entanglement and quantum mutual information to evaluate total correlations, we analyze the evolution of these quantum resources under symmetric and asymmetric photon‐environment couplings. Key tunable parameters – including the relative weighting of the two peaks in the double‐Gaussian environmental frequency profile, refractive index difference, spectral width, and overall frequency distribution – are explored within experimentally realistic ranges achievable with photonic platforms such as Fabry–Pérot cavities. Our results provide that non‐Markovian environments substantially enhance the robustness of entanglement, exhibiting prominent oscillatory revivals under symmetric peak weightings, whereas more asymmetric configurations result in faster monotonic decay. These findings propose practical strategies, such as optimized cavity configurations, to suppress decoherence and prolong the lifetime of multipartite quantum correlations, thereby supporting the development of more resilient photonic quantum states for quantum technologies.